Carburetor



- 1935. c. J. GRACE 2,0245% I CARBURETOR Filed Nov. 28, 1933 :5 Sheets-Sheet 1 C. J. GRACE CARBURETOR 5 Sheets-Sheet 2 Filed Nov. 28, 1933 c. J. GRACE 2,6243% CARBURETOR Filed Nov. 28, 1933 3 SheetsSheet 5 Dec. 17, 1935 v Patented Dec. 17, 1935 PATENT QFFICE 2,024,638 .OARBURETOR Charles Jeens Grace, London, England Application November 28, 1933, Serial No. 700,133 In Great Britain January 11, 1933 This invention relates to carburetors for use with internal combustion engines and more particularly to carburetors of the type in which the fuel inlet is located between thethrottle valve and the engine intake manifold.

In the present specification, as in my co-pending specification No. 643,250, filed November 18, 1932, the carburetor described is of the type wherein the jets or fuel orifices for-thej supply of petrol are located on the engine or suction side of an air throttle valve as distinct from the more common type of carburetor wherein a mixture throttle valve is located on the engine or suction side of the fuel orifices. The appended claims therefore are intended 'to define carburetors wherein the throttle valve .controls air intake as distinct from the more usual carburetors wherein the throttle valve controls the flow of-fuel-air mixture to the engine.

The present invention has for its main object to provide improvements in carburetors as disclosed in my said specification. As will be seen from the description which follows, the present invention provides improved carburetors wherein a suction opened air throttle valve,.which is the only throttle valve in the carburetor, and the opening of which is manually limited, is so arranged as to act not only as an unbalanced throttle valve as setforth in my copending specification hereinbefore referred to, but alsouasthe moving member of what is ineffect an automatically varying choke.

One form of construction of carburetor inaccordance with the present invention is illustrated in the accompanying drawings in which Figure 1 is aside elevation; Figure 2 is a sectional elevation taken through the centre line of the air intake tube; Figure 3 is anend elevation ,of the arrangement shown in Figures 1 and 2 and showing the carburetor as regarded from the engine end; Figure 4 is an end elevation ,of the carburetor regarded from the air intake end and Figures 5 and6 are sectional detail views.

Referring to the drawings an air intake tube ill of rectangular cross-section over the major portion of its length has pivotally mounted about an axis l2 lying inone wall of said tube In a throttle vane l4 of rectangular outline and in section curved over towards the engine as shown. With the throttle valve arranged in this way, it

will be seen that there is always a welldefined throat or choke' formed between the curved surfaceof thethrottle'vane andtheupper side of the tube ll]. Thewall' of-the tubeadjacent thepivot '12 is recessed as shown .at- It to .re-

ceive the curved portion of the vane 14 when the throttle is in the fully open position so that in this position thethrottle vane offers substantially no restriction to the fiow of air through thetube.

The fuel spraying orifice is formed in a block 5 l8 mounted in the top wall, of the tube IO and consists-of a narrow transverse sliti20 communieatin with ;a transversely drilled passage 22 plugged at each end as shown in Figure 5. Drilledgvertically through the block is a pair of passages 24 which communicate with the passage 22 and thesepassagesyu communicate with the atmosphere through air-bleed ducts 26 which open into a horizontal drilling 28 which is partially closed by means of an annular plug 39 whose internal ;diameter determines the amount of air bleed. A central vertical passage 32 has screwed into the upper end thereof a fuel jet 34 .;andz az;horizontal. drilling 136= plugged at :38 passes'through the-passage 32 and communicates with fuel ducts 40.

Surmounting the block i8 is a cap member 42 recessed as shown at .44 andhaving an upwardly extending portion 46. On the top of the cap member 42 issecured a cylinder 48 by means of screws which serve also to retain in position the cap 42. Within the cylinder 48 is arranged a recessed piston '59 to which is secured a hollow sleeve 52 which is a working fit in a central borin 'in the upwardly extending portion 46 of the 03 1 142. This sleeve is of such length that when the piston is near the bottom of the cylinder 48 the end of the sleeve 52 makes contact with the rirnof the jet :34 thus effectively cutting off communication between the passage 32 and the passage 24 via the recess 44. Clamped within the sleeve 52 by means of a grub-screw 54 is a modulating pin 55 Which, as the piston rises andi-falls within the cylinder (as described later) 'controls theefiectivearea of the fuel jet 34.

The upper end of.:cyl i nder 48 is put into communication with the induction pipe at any point (not shown) on theengineflside of the throttle by means of, a passage .filifformed in the wall of the tube Iii and a pipe f fill'which is coupled to a nipple 62 screwed into said wall of the tube It], as shown.

*;:The ylinder 48 sl ghtly verhan s the block l8 in side vieW-(seFigure-Z) (thus allowing access of air-to the underside of piston and 50 a vertical -push-rod-64 attached to the piston, as shown,=-by--a screw 66 passes between the cylinder and block at the rear "sideja-nd V terminates in -a :fork -68 =by'--means of -which 'it -is coupled through a-link -10 to an 'arm 12 fast on the throttle vane spindle. The link 10 is hinged to the arm 12 by means of a pin 14 which can be adjusted in a slot 16 in the arm I2. The link 10 passes through narrow slots 18 formed in the upper and lower walls of the tube I0.

The throttle vane spindle carries at one end thereof an arm rigidly secured thereto, and to which is attached by means of a tensioning device 82 one end of a spring 84 the other end of which is anchored to the body of the carburetor. On the other end of the throttle vane spindle is mounted a control lever 86 which is so arranged that the degree to which the throttle vane is free to open, is determined by the position of said con-'- i trol lever, as set forth in the parent specification i. e. the control lever can operate positively to" close the throttle but not tolope'n it. a

The lower face of the block l8 which projects into the tube [0 is approximately wedge shaped, as shown, the surface 90 being radius'e'd about the axis l2 as centre, so that the initialmovement of the throttle has :no effect as regards admission of air. A slight' depression 92 is formed in the-upper edge of the vane l4 to permit a small fiow of air for slow running. I A relief valve, consisting of a flap 94 hinged at 96 and held closedby means of a spring 98, is located intherecessed portion I6 of the tube In operation, assuming the control lever to'be in the fully open position, the throttle vane is free to take up any position between the fully open and fully closed positionsas determined by conditions of air flow or engine suction. The position of thethrottle vane is determined not only by air flow past it acting directly upon it but also by thedegree of suction acting upon the top of piston 50. The piston 56 sliding in cylinder 48 will act as a dash-pot so long as the force acting directly on the throttle 'valvea'nd tending to open it against the pull of spring'84 is greater than the force exerted due to suction acting on the topof the piston 50 but the bore of the passage 58 or thepipe 60 leading thereto and'the area of the piston 50 are such'that a point is reached when the piston and cylinder act not as a dash-pot but as a device for assisting opening of the throttle valve in dependence upon suction. a

It will be seen that as the piston .50 rises and falls within the cylinder 48 in dependence upon throttle opening the effective area of jet 34 is varied by the modulating pin 56. Petrol or fuel entering the carburetor via duct 40,passes into passage 36; through the jet 34; through the recess 44; down the passages 24; and into the passage 22.

In cases where the fuel is supplied to the fuel jet 34 under a steady positive head (this is not the case in the carburetor illustratedrand a full so-called dribble jet effectis requiredthe air-bleed ducts 26 are made of such size that substantially atmospheric pressureis maintained upon the fuel passing to the jet and the flow through the jet 34 is thus made practically independent ofthe suction effect in the tube ID for any degree of throttle opening. In such cases, the arrangement of the ducts 26 is exactly the same as shown in the accompanying drawings, with the exception that the cross sectional area of the ducts is slightly larger than as shown in the drawings. Of course, if ,desireda par-i tial or modified dribble effect ,may be obtained,

i. e. the air bleeds may be madeiofsuchgsize that the fuel flow is affected substantially by suction on the jet. In any event the air bleeds 26 are made sufficiently large that if excessive suction is developed in the induction pipe (e. g. if the engine runs fast with light load) that excessive suction will act in the main upon the air supply through the bleeds rather than on the petrol supply and thus undesired and unnecessary enriching of the mixture under light load conditions will be avoided. Where the dribble jet effect is not employed the air bleeds may be of such size relative to the jet area that a desired fuel flow is obtained from the jet as a result of suction thereon. The curving of the throttle vane and the, position of the fuel spraying orifice, as shown, ensures that fuel always enters the. tube If! at a point of approximately maximum' air velocity.

If the engine is running fast and it is desired to close the throttle suddenly the suction on the engine side of the throttle vane may render it diflicult to actuate the throttle lever and the relief valve spring is so adjusted that if an excessive suctionforce occurs the flap 94 will open and permitreduction of the suction force tending to hold the throttle open.

"The carburetor illustrated in the drawings is shown as being provided with a fioat chamber so positioned as to give no head at the jet. The provision of a float chamber is however optional. In the illustrated carburetor petrol is positively shut off in the closed position of thethrottle by means of the sleeve 52'seating on theirim of the jet 34.

The float chamber, when provided, is bolted on totheiside of the block 3, as shown.

'In operation, suction in the right hand end of the tube I 0 causes the throttle valve 14 to open, air then flowing through the tube from left to right, as viewed in Figure 2. Air also will 40 enter through the apertured plug 36 and will flow through the drilling 28, the ducts 26, the passages 24, the passage 22 and the slit 26 to'the interior of the tube l0. Opening-movement of the throttle valve having lifted the sleeve.52 off the rim of the jet 34, fuel will enter through the duct. 40 and will flow upwardly through the jet 34, horizontally through the recess 44, downwardly through the passages 24 into the passage 22 and thence out through the slit 20 into the tube I0;

What I claim is:

1. In a carburetor, the combination of a suction-responsive throttle valve pivotally mounted about an axis which-is closely adjacent one edge of said valve so that the suction effect on said valvetends to open it and substantially all occurs on one side of said axis so that air admitted past said "valve must substantially all pass on one side thereof, said valve being so shaped as to be convex on the side facing towards incoming air and being the only throttle valve in the carburetor, a manually adjustable stop member for limiting the degree of'opening ofsaid valve, at least one fuel orifice located to admit fuel into the air-stream passed by said throttle .valve, said orifice being also so located as to be in a position of high velocity air flow pastsaid throttle whereby said throttle'valveacts not only'as an unbalanced throttle valve butalso as the, moving member of what is in effect an automatically varying choke, a cylinder; and'a piston therein, said piston'being operatively associated with the throttle valve, and said cylinder having a conduit leading -fromabove the pistonand adapted to 7 communicate with the intake manifold of an associated engine at a point of low pressure between said throttle valve and said engine.

2. In a carburetor, the combination of a suc- 5 tion-responsive throttle valve pivotally mounted about an axis which is closely adjacent one edge of said valve so that the suction effect on said valve tends to open it and substantially all ocours on one side of said axis so that air admitted past said valve must substantially all pass on one side thereof, said valve being so shaped as to be convex on the side facing towards incoming air and being the only throttle valve in the carburetor, a manually adjustable stop member for limiting the degree of opening of said valve, at

least one fuel orifice located to admit fuel into the air stream passed by said throttle valve, said orifice being also so located as to be in a position of high velocity air flow past said throttle whereby said throttle valve acts not only as an unbalanced throttle valve but also as the moving member of what is in effect an automatically varying choke, means for automatically controlling the supply of fuelto the fuel orifice in dependence upon the degree of opening of the throttle valve, means for applying substantially atmospheric pressure to fuel passing to said orifice, and means for supplying fuel to said orifice under steady positive head whereby a so-called dribble jet 3O effect is obtained.

3. In a carburetor, the'combination of a suction-responsive throttle valve pivotally mounted about an axis which is closely adjacent one edge of said valve so that the suction effect on said valve tends toopen it and substantially all oc-' ours on one side of said axis so that air admitted past said valve must substantially all pass on one side thereof, said valve being so shaped as to be -convex on the side facing towards incoming air 40 and being the only throttle valve in the carburetor, a manually adjustable stop member for limiting the degree of opening of said valve, at

least one fuel orifice located to admit fuel into the air stream passed bysaid throttle valve, said 5 orifice being also so located as to be in a position of high velocity air flow past said throttle where'- by said throttle valve acts not only as an unbalanced throttle valve but also as the moving mem- 50 ber of what is in effect an automatically varying choke, means for automatically controlling the supply of fuel to the fuel orifice in dependence upon the degree of opening of the throttle valve, and at least one air bleeding duct communicat- 5 ing with a fuel duct or ducts between the automatic fuel supply controlling means and said fuel orifice.

4. In a carburetor, the combination of a suction-responsive throttle valve pivotally mounted about an axis which is closely adjacent one edge 5 of said valve so that the suction effect on said valve tends to open it and substantially all occurs on one side of said axis so that air admitted past said valve must substantially all pass on one side thereof, said valve being so shaped as to 10 be convex on the side facing towards incoming air and being the only throttle valve in the carburetor, a manually adjustable stop member for limiting the degree of opening of said valve, a single fuel orifice comprising a narrow slit ex- 15 tending transversely of the air intake tube of the carburetor adjacent one side of the tube, said orifice being also so located as to be in a position of high velocity air fiow past said throttle whereby said throttle valve acts not only as an unbal- 20 anced throttle valve but also as the moving member of what is in eiTect an automatically varying choke, and means for automatically controlling the supply of fuel to the fuel orifice in dependence upon the degree of opening of the throttle 25 valve.

5. In a carburetor, the combination of a suction-responsive throttle valve pivotally mounted about an axis which is closely adjacent one edge of said valve so that the suction effect on said 30 valve tends to open it and substantially all ocours on one side of said axis so that air admitted past said valve must substantially all pass on one side thereof, said valve being so shaped as to be convex on the side facing towards incoming air 35 and being the only throttle valve in the carburetor, a manually adjustable stop member for limiting the degree of opening of said valve, at least one fuel orifice located to admit fuel into the air stream passed by said throttle valve, said 4o I orifice being also so located as to be in a position of high velocity air flow past said throttle whereby said throttle valve acts not only as an unbalanced throttle valve but also as the moving member of what is in effect an automatically varying choke, means for automatically controlling the supply of fuel to the fuel orifice in dependence upon the degree of opening of the throttle valve, and suction-operated auxiliary air inlet valve means adapted to admit air to the carburetor at a point on the engine side of said throttle valve if a suction exceeding a predetermined amount is built up on the engine side of said throttle valve.

CHARLES JEENS GRACE. 

